Add transparency to tracer trails

joshburkart · Jul 2, 2024 · 5d8bea4 · 5d8bea4
1 parent 84be3ed
commit 5d8bea4
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Showing 3 changed files with 66 additions and 24 deletions.
diff --git a/tsunami/src/geom.rs b/tsunami/src/geom.rs
@@ -8,6 +8,7 @@ use crate::{
 
 const TRACER_STEP: usize = 3;
 const TRACER_HISTORY_LENGTH: usize = TRACER_STEP.pow(3);
+pub const TRACER_TAIL_LENGTH: usize = TRACER_HISTORY_LENGTH / TRACER_STEP;
 
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum GeometryType {

diff --git a/tsunami/src/lib.rs b/tsunami/src/lib.rs
@@ -255,13 +255,20 @@ pub async fn run() {
         geometry: InstancedMesh::new(
             &context,
             &PointCloud {
-                positions: Positions::F64(rendering_data.tracer_points),
+                positions: Positions::F64(vec![]),
                 colors: None,
             }
             .into(),
             &point_mesh,
         ),
-        material: ColorMaterial::default(),
+        material: ColorMaterial::new_transparent(
+            &context,
+            &CpuMaterial {
+                roughness: 1.,
+                albedo: Srgba::WHITE,
+                ..Default::default()
+            },
+        ),
     };
 
     let mut tsunami_hint_circle_object = Gm {
@@ -418,6 +425,7 @@ pub async fn run() {
                         positions: Positions::F32(
                             rendering_data
                                 .tracer_points
+                                .points
                                 .into_iter()
                                 .map(|point| {
                                     rotation.transform_vector(Vector3 {
@@ -428,7 +436,22 @@ pub async fn run() {
                                 })
                                 .collect(),
                         ),
-                        colors: None,
+                        colors: Some(
+                            rendering_data
+                                .tracer_points
+                                .positions
+                                .into_iter()
+                                .map(|position| {
+                                    Srgba::new(
+                                        u8::MAX,
+                                        u8::MAX,
+                                        u8::MAX,
+                                        // Add transparency based on position in tracer's trail.
+                                        u8::MAX / geom::TRACER_TAIL_LENGTH as u8 * position as u8,
+                                    )
+                                })
+                                .collect(),
+                        ),
                     }
                     .into(),
                     &point_mesh,

diff --git a/tsunami/src/render.rs b/tsunami/src/render.rs
@@ -5,7 +5,7 @@ use three_d::{CpuMesh, Indices, Positions, Vector3};
 #[derive(Clone)]
 pub struct RenderingData {
     pub quadrature_points: Vec<Vector3<Float>>,
-    pub tracer_points: Vec<Vector3<Float>>,
+    pub tracer_points: TracerPoints,
     pub mesh: CpuMesh,
 }
 
@@ -147,25 +147,31 @@ impl SphereRenderable {
         points
     }
 
-    fn make_tracer_points(&self, height_exaggeration_factor: Float) -> Vec<Vector3<Float>> {
-        self.tracer_points_history_mu_phi
+    fn make_tracer_points(&self, height_exaggeration_factor: Float) -> TracerPoints {
+        let (points, positions) = self
+            .tracer_points_history_mu_phi
             .iter()
+            .enumerate()
             .zip(&self.tracer_heights_history)
-            .map(|(tracer_points_mu_phi, tracer_heights)| {
+            .map(|((position, tracer_points_mu_phi), tracer_heights)| {
                 tracer_points_mu_phi
                     .axis_iter(nd::Axis(1))
                     .zip(tracer_heights.iter())
-                    .map(|(point_mu_phi, &height)| {
-                        self.make_point(
-                            point_mu_phi[[0]],
-                            point_mu_phi[[1]],
-                            height,
-                            height_exaggeration_factor,
+                    .map(move |(point_mu_phi, &height)| {
+                        (
+                            self.make_point(
+                                point_mu_phi[[0]],
+                                point_mu_phi[[1]],
+                                height,
+                                height_exaggeration_factor,
+                            ),
+                            position,
                         )
                     })
             })
             .flatten()
-            .collect()
+            .unzip();
+        TracerPoints { points, positions }
     }
 
     fn make_point(
@@ -289,25 +295,31 @@ impl TorusRenderable {
         points
     }
 
-    fn make_tracer_points(&self, height_exaggeration_factor: Float) -> Vec<Vector3<Float>> {
-        self.tracer_points_history_theta_phi
+    fn make_tracer_points(&self, height_exaggeration_factor: Float) -> TracerPoints {
+        let (points, positions) = self
+            .tracer_points_history_theta_phi
             .iter()
+            .enumerate()
             .zip(&self.tracer_heights_history)
-            .map(|(tracer_points_mu_phi, tracer_heights)| {
+            .map(|((position, tracer_points_mu_phi), tracer_heights)| {
                 tracer_points_mu_phi
                     .axis_iter(nd::Axis(1))
                     .zip(tracer_heights.iter())
-                    .map(|(point_mu_phi, &height)| {
-                        self.make_point(
-                            point_mu_phi[[0]],
-                            point_mu_phi[[1]],
-                            height,
-                            height_exaggeration_factor,
+                    .map(move |(point_mu_phi, &height)| {
+                        (
+                            self.make_point(
+                                point_mu_phi[[0]],
+                                point_mu_phi[[1]],
+                                height,
+                                height_exaggeration_factor,
+                            ),
+                            position,
                         )
                     })
             })
             .flatten()
-            .collect()
+            .unzip();
+        TracerPoints { points, positions }
     }
 
     fn make_point(
@@ -326,3 +338,9 @@ impl TorusRenderable {
                     * (-phi.cos() * radially_out + phi.sin() * Vector3::unit_z()))
     }
 }
+
+#[derive(Clone)]
+pub struct TracerPoints {
+    pub points: Vec<Vector3<Float>>,
+    pub positions: Vec<usize>,
+}